A novel non-transcriptional pathway mediates the proconvulsive effects of interleukin-1beta.
Interleukin-1beta (IL-1beta) is overproduced in human and rodent epileptogenic tissue and it exacerbates seizures upon brain application in rodents. Moreover, pharmacological prevention of IL-1beta endogenous synthesis, or IL-1 receptor blockade, mediates powerful anticonvulsive actions indicating a significant role of this cytokine in ictogenesis. The molecular mechanisms of the proconvulsive actions of IL-1beta are not known. We show here that EEG seizures induced by intrahippocampal injection of kainic acid in C57BL6 adult mice were increased by 2-fold on average by pre-exposure to IL-1beta and this effect was blocked by 3-O-methylsphingomyelin (3-O-MS), a selective inhibitor of the ceramide-producing enzyme sphingomyelinase. C2-ceramide, a cell permeable analog of ceramide, mimicked IL-1beta action suggesting that ceramide may be the second messenger of the proconvulsive effect of IL-1beta. The seizure exacerbating effects of either IL-1beta or C2-ceramide were dependent on activation of the Src family of tyrosine kinases since they were prevented by CGP76030, an inhibitor of this enzyme family. The proconvulsive IL-1beta effect was associated with increased Tyr(418) phosphorylation of Src-family of kinases indicative of its activation, and Tyr(1472) phosphorylation of one of its substrate, the NR2B subunit of the N-methyl-d-aspartate receptor, which were prevented by 3-O-MS and CGP76030. Finally, the proconvulsive effect of IL-1beta was blocked by ifenprodil, a selective NR2B receptor antagonist. These results indicate that the proconvulsive actions of IL-1beta depend on the activation of a sphingomyelinase- and Src-family of kinases-dependent pathway in the hippocampus which leads to the phosphorylation of the NR2B subunit, thus highlighting a novel, non-transcriptional mechanism underlying seizure exacerbation in inflammatory conditions.
Balosso
Silvia
S
Department of Neuroscience, Laboratory of Experimental Neurology, Mario Negri Institute for Pharmacological Research, Milan, Italy.
Maroso
Mattia
M
Sanchez-Alavez
Manuel
M
Ravizza
Teresa
T
Frasca
Angelisa
A
Bartfai
Tamas
T
Vezzani
Annamaria
A
D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D002518:Ceramides / Q000502:physiology; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D053583:Interleukin-1beta / Q000378:metabolism / Q000502:physiology* / Q000633:toxicity; D007608:Kainic Acid; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010766:Phosphorylation; D017472:Receptors, Interleukin-1 / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D011994:Recombinant Proteins / Q000633:toxicity; D012640:Seizures / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology*; D015398:Signal Transduction / Q000187:drug effects; D013108:Sphingomyelin Phosphodiesterase / Q000502:physiology; D019061:src-Family Kinases / Q000502:physiology
D002518:Ceramides; D053583:Interleukin-1beta; C121001:NR2B NMDA receptor; D017472:Receptors, Interleukin-1; D016194:Receptors, N-Methyl-D-Aspartate; D011994:Recombinant Proteins; D019061:src-Family Kinases; D013108:Sphingomyelin Phosphodiesterase; D007608:Kainic Acid